U.S. patent number 7,625,976 [Application Number 11/327,894] was granted by the patent office on 2009-12-01 for room temperature curable organopolysiloxane composition.
This patent grant is currently assigned to Momemtive Performance Materials Inc.. Invention is credited to Vikram Kumar, Shayne J. Landon, Edward J. Nesakumar, Indumathi Ramakrishnan, David A. Williams.
United States Patent |
7,625,976 |
Landon , et al. |
December 1, 2009 |
Room temperature curable organopolysiloxane composition
Abstract
This invention relates to a room temperature curable composition
containing, inter alia, diorganopolysiloxane(s) and organic
nanoclay(s), the cured composition exhibiting low permeability to
gas(es).
Inventors: |
Landon; Shayne J. (Ballston
Lake, NY), Williams; David A. (Ganesvoort, NY), Kumar;
Vikram (Bangalore, IN), Nesakumar; Edward J.
(Bangalore, IN), Ramakrishnan; Indumathi (Bangalore,
IN) |
Assignee: |
Momemtive Performance Materials
Inc. (Albany, NY)
|
Family
ID: |
38169547 |
Appl.
No.: |
11/327,894 |
Filed: |
January 9, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070173596 A1 |
Jul 26, 2007 |
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Current U.S.
Class: |
524/588; 528/34;
525/464; 525/446; 525/431; 525/393; 525/104; 525/100; 524/448;
524/447; 524/445 |
Current CPC
Class: |
C09D
183/04 (20130101); C08L 83/04 (20130101); C08L
83/04 (20130101); C08L 2666/54 (20130101); C08L
83/04 (20130101); C08L 83/00 (20130101); C09D
183/04 (20130101); C08L 83/00 (20130101); C09D
183/04 (20130101); C08L 2666/54 (20130101); C08G
77/16 (20130101); C08K 5/5419 (20130101); C08G
77/80 (20130101); C08K 3/34 (20130101) |
Current International
Class: |
C08L
83/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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4136689 |
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May 1992 |
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DE |
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0220809 |
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May 1987 |
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EP |
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0520777 |
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Dec 1992 |
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EP |
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0857761 |
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Aug 1998 |
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EP |
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0994151 |
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Mar 2006 |
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EP |
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2249552 |
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May 1992 |
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GB |
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WO 97/31057 |
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Aug 1997 |
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WO |
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WO99/45072 |
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Sep 1999 |
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WO |
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WO 02064676 |
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Aug 2002 |
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WO |
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Other References
Peter C. LeBaron et al., "Clay Nanolayer Reinforcement of a
Silicone Elastomer", 2001. cited by other .
Shelly D. Burnside et al., "Nanostructure and Properties of
Polysiloxane-Layered Silicate Nanocomposites", Mar. 28, 2000. cited
by other .
K. Mizoguchi et al., "Miscibility and gas permeability of poly
(ethylene-co-5,4 mol% 3,5,5-trimethylhexyl methacrylate)-
polydimethyl-siloxane blends", 1997. cited by other .
Y. Geerts et al., "Morphology and Permeability of Polymer Blends-I.
Crosslinked EPDM-Silicone Blends", 1996. cited by other.
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Primary Examiner: Zimmer; Marc S
Attorney, Agent or Firm: Vicari; Dominick G.
Claims
What is claimed is:
1. A curable composition comprising: a) at least one
silanol-terminated diorganopolysiloxane; b) at least one
alkylsilicate crosslinker having the formula:
(R.sup.14O)(R.sup.15O)(R.sup.16O)(R.sup.17O)Si where R.sup.14,
R.sup.15, R.sup.16 and R.sup.17 are chosen independently from
monovalent C.sub.1 to C.sub.60 hydrocarbon radicals; c) at least
one catalyst for the crosslinking reaction; d) at least one
orcianic nanoclay; and, optionally; and e) at least one solid
polymer having a permeability to gas that is less than the
permeability of the crosslinked diorganopolysiloxane(s).
2. The composition of claim 1 wherein catalyst (c) is a tin
catalyst.
3. The composition of claim 2 wherein the tin catalyst is selected
from the group consisting of dibutyltindilaurate,
dibutyltindiacetate, dibutyltindimethoxide, tinoctoate,
isobutyltintriceroate, dibutyltinoxide, dibutyltin
bis-diisooctylphthalate, bis-tripropoxysilyl dioctyltin, dibutyltin
bis-acetylacetone, silylated dibutyltin dioxide, carbomethoxyphenyl
tin tris-uberate, isobutyltin triceroate, dimethyltin dibutyrate,
dimethyltin di-neodecanoate, triethyltin tartarate, dibutyltin
dibenzoate, tin oleate, tin naphthenate,
butyltintri-2-ethylhexylhexoate, tinbutyrate, diorganotin bis
.beta.-diketonates and mixtures thereof.
4. The composition of claim 1 wherein the nanoclay portion of
organic nanoclay (d) is selected from the group consisting of
montmorillonite, sodium montmorillonite, calcium montmorillonite,
magnesium montmorillonite, nontronite, beidellite, volkonskoite,
laponite, hectorite, saponite, sauconite, magadite, kenyaite,
sobockite, svindordite, stevensite, vermiculite, halloysite,
aluminate oxides, hydrotalcite, illite, rectorite, tarosovite,
ledikite, kaolinite and, mixtures thereof.
5. The composition of claim 1 wherein the organic portion of
organic nanoclay (d) is at least one tertiary amine compound
R.sup.3R.sup.4R.sup.5N and/or quarternary ammonium compound
R.sup.6R.sup.7R.sup.8N.sup.+X.sup.- wherein R.sup.3, R.sup.4,
R.sup.5, R.sup.6, R.sup.7 and R.sup.8 each independently is an
alkyl, alkenyl or alkoxy silane group of up to 60 carbon atoms and
X is an anion.
6. The composition of claim 4 wherein the nanoclay portion of
organic nanoclay (d) is modified with ammonium, primary
alkylammonium, secondary alkylammonium, tertiary alkylammonium
quaternary alkylammonium, phosphonium derivatives of aliphatic,
aromatic or arylaliphatic amines, phosphines or sulfides or
sulfonium derivatives of aliphatic, aromatic or arylaliphatic
amines, phosphines or sulfides.
7. The composition of claim 1 wherein solid polymer (e) is selected
from the group consisting of low density polyethylene, very low
density polyethylene, linear low density polyethylene, high density
polyethylene, polypropylene, polyisobutylene, polyvinyl acetate,
polyvinyl alcohol, polystyrene, polycarbonate, polyester, such as,
polyethylene terephthalate, polybutylene terephthalate,
polyethylene napthalate, glycol-modified polyethylene
terephthalate, polyvinylchloride, polyvinylidene chloride,
polyvinylidene fluoride, thermoplastic polyurethane, acrylonitrile
butadiene styrene, polymethylmethacrylate, polyvinyl fluoride,
polyamides, polymethylpentene, polyimide, polyetherimide, polether
ether ketone, polysulfone , polyether sulfone, ethylene
chlorotrifluoroethylene, polytetrafluoroethylene, cellulose
acetate, cellulose acetate butyrate, plasticized polyvinyl
chloride, ionomers, polyphenylene sulfide, styrene-maleic
anhydride, modified polyphenylene oxide, ethylene-propylene rubber,
polybutadiene, polychloroprene, polyisoprene, polyurethane,
styrene-butadiene-styrene, styrene-ethylene-butadiene-styrene,
polymethylphenyl siloxane and mixtures thereof.
8. The composition of claim 1 which further comprises at least one
optional component selected from the group consisting of adhesion
promoter, surfactant, colorant, pigment, plasticizer, filler other
than organic nanoclay, antioxidant, UV stabilizer, and biocide.
9. The composition of claim 8 wherein the adhesion promoter is
selected from the group consisting of
n-2-aminoethyl-3-aminopropyltrimethoxysilane,
1,3,5-tris(trimethoxysilylpropyl)isocyanurate,
.gamma.-aminopropyltriethoxysilane,
.gamma.-aminopropyltrimethoxysilane, aminopropyltrimethoxysilane,
bis-.gamma.-trimethoxysilypropyl)amine,
N-Phenyl-.gamma.-aminopropyltrimethoxysilane,
triaminofunctionaltrimethoxysilane,
.gamma.-aminopropylmethyldiethoxysilane,
.gamma.-aminopropylmethyldiethoxysilane,
methacryloxypropyltrimethoxysilane,
methylaminopropyltrimethoxysilane,
.gamma.-glycidoxypropylethyldimethoxysilane,
.gamma.-glycidoxypropyltrimethoxysilane,
.gamma.-glycidoxyethyltrimethoxysilane,
.beta.-(3,4-epoxycyclohexyl)propyltrimethoxysilane,
.beta.(3,4-epoxycyclohexyl) ethylmethyldimethoxysilane,
isocyanatopropyltriethoxysilane,
isocyanatopropylmethyldimethoxysilane,
.beta.-cyanoethyltrimethoxysilane,
.gamma.-acryloxypropyltrimethoxysilane,
.gamma.-methacryloxypropylmethyldimethoxysilane,
4-amino-3,3,-dimethylbutyltrimethoxysilane,
n-ethyl-3-trimethoxysilyl-2-methylpropanamine, and mixtures
thereof.
10. The composition of claim 8 wherein the surfactant is a nonionic
surfactant selected from the group consisting of polyethylene
glycol, polypropylene glycol, ethoxylated castor oil, oleic acid
ethoxylate, alkylphenol ethoxylates, copolymers of ethylene oxide
and propylene oxide and copolymers of silicones and polyethers,
copolymers of silicones and copolymers of ethylene oxide and
propylene oxide and mixtures thereof.
11. The composition of claim 10 wherein the non-ionic surfactant is
selected from the group consisting of copolymers of ethylene oxide
and propylene oxide, copolymers of silicones and polyethers,
copolymers of silicones and copolymers of ethylene oxide and
propylene oxide and mixtures thereof.
12. The composition of claim 8 wherein the filler other than the
organic nanoclay is selected from the group consisting of calcium
carbonate, precipitated calcium carbonate, colloidal calcium
carbonate, calcium carbonate treated with compounds stearate or
stearic acid, fumed silica, precipitated silica, silica gels,
hydrophobized silicas, hydrophilic silica gels, crushed quartz,
ground quartz, alumina, aluminum hydroxide, titanium hydroxide,
clay, kaolin, bentonite montmorillonite, diatomaceous earth, iron
oxide, carbon black and graphite, mica, talc, and mixtures
thereof.
13. The cured composition of claim 1.
14. The cured composition of claim 7.
15. The cured composition of claim 8.
16. The composition of claim 13 exhibiting an argon permeability
coefficient of not greater than about 900 barrers.
17. The composition of claim 14 exhibiting an argon permeability
coefficient of not greater than about 900 barrers.
18. The composition of claim 15 exhibiting an argon permeability
coefficient of not greater than about 900 barrers.
19. The composition of claim 1 wherein the composition is a curable
sealant.
20. The composition of claim 1 wherein the composition is a cured
sealant.
21. The composition of claim 13 wherein the composition is a
curable sealant.
22. The composition of claim 13 wherein the composition is a cured
sealant.
23. The composition of claim 9 wherein the composition is a cured
adhesive.
24. The composition of claim 13 wherein the composition is a
curable adhesive.
25. The composition of claim 13 wherein the composition is a cured
adhesive.
Description
FIELD OF THE INVENTION
This invention relates to a room temperature curable composition
exhibiting, when cured, low permeability to gas(es).
BACKGROUND OF THE INVENTION
Room temperature curable (RTC) compositions are well known for
their use as sealants. In the manufacture of Insulating Glass Units
(IGU), for example, panels of glass are placed parallel to each
other and sealed at their periphery such that the space between the
panels, or the inner space, is completely enclosed. The inner space
is typically filled with a gas or mixture of gases of low thermal
conductivity, e.g. argon. Current room temperature curable silicone
sealant compositions, while effective to some extent, still have
only a limited ability to prevent the loss of insulating gas from
the inner space of an IGU. Over time, the gas will escape reducing
the thermal insulation effectiveness of the IGU to the vanishing
point.
A need therefore exists for an RTC composition of reduced gas
permeability compared to that of known RTC compositions. When
employed as the sealant for an IGU, an RTC composition of reduced
gas permeability will retain the intra-panel insulating gas for a
longer period of time compared to that of a more permeable RTC
composition and will therefore extend the insulating properties of
the IGU over a longer period of time.
SUMMARY OF THE INVENTION
The present invention is based on the discovery that curable
silanol-terminated diorganopolysiloxane combined with filler of a
certain type upon curing exhibits reduced permeability to gas. The
composition is especially suitable for use as a sealant where high
gas barrier properties together with the desired characteristics of
softness, processability and elasticity are important performance
criteria.
In accordance with the present invention, there is provided a
curable composition comprising: a) at least one silanol-terminated
diorganopolysiloxane; b) at least one crosslinker for the
silanol-terminated diorganopolysiloxane(s); c) at least one
catalyst for the crosslinking reaction; d) at least one organic
nanoclay; and, optionally, e) at least one solid polymer having a
permeability to gas that is less than the permeability of the
crosslinked diorganopolysiloxane(s).
When used as a gas barrier, e.g., in the manufacture of an IGU, the
foregoing composition reduces the loss of gas(es) thus providing a
longer service life of the article in which it is employed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graphic presentation of permeability data for the
sealant compositions of Comparative Examples 1-2 and Examples 1-3
and 5-8.
FIG. 2 is a graphic presentation of permeability data for the
sealant compositions of Comparative Examples 1-2 and Examples 4 and
9.
DETAILED DESCRIPTION OF THE INVENTION
The curable sealant composition of the present invention is
obtained by mixing (a) at least one diorganopolysiloxane, (b) at
least one crosslinker for the diorganopolysiloxane(s), (c) at least
one catalyst for the crosslinking reaction, (d) at least one
organic nanoclay and, optionally, (e) at least one solid polymer
having a permeability to gas that is less than the permeability of
the crosslinked diorganopolysiloxane(s), the composition following
curing exhibiting low permeability to gas(es).
The compositions of the invention are useful for the manufacture of
sealants, coatings, adhesives, gaskets, and the like, and are
particularly suitable for use in sealants intended for insulating
glass units.
The viscosity of the silanol-terminated diorganopolysiloxane that
is employed in the curable composition of the invention can vary
widely and advantageously ranges from about 1,000 to about 200,000
cps at 25.degree. C.
Suitable silanol-terminated diorganopolysiloxanes (a) include those
of the general formula: M.sub.aD.sub.bD'.sub.c wherein "a" is 2,
and "b" is equal to or greater than 1 and "c" is zero or positive;
M is (HO).sub.3-x-yR.sup.1.sub.xR.sup.2.sub.ySiO.sub.1/2 wherein
"x" is 0, 1 or 2 and "y" is either 0 or 1, subject to the
limitation that x+y is less than or is equal to 2, R.sup.1 and
R.sup.2 each independently is a monovalent hydrocarbon group up to
60 carbon atoms; D is R.sup.3R.sup.4SiO.sub.2/2 wherein R.sup.3 and
R.sup.4 each independently is a monovalent hydrocarbon group up to
60 carbon atoms; and D' is R.sup.5R.sup.6SiO.sub.2/2 wherein
R.sup.5 and R.sup.6 each independently is a monovalent hydrocarbon
group up to 60 carbon atoms.
Suitable crosslinkers (b) for the silanol-terminated
diorganopolysiloxane(s) present in the composition of the invention
include alkylsilicates of the general formula:
(R.sup.14O)(R.sup.15O)(R.sup.16O)(R.sup.17O)Si wherein R.sup.14,
R.sup.15, R.sup.16 and R.sup.17 each independently is a monovalent
hydrocarbon group up to 60 carbon atoms. Crosslinkers of this type
include, n-propyl silicate, tetraethylortho silicate and
methyltrimethoxysilane and similar alkyl-substituted alkoxysilane
compounds, and the like.
Suitable catalysts (c) for the crosslinking reaction of the
silanol-terminated diorganopolysiloxane(s) can be any of those
known to be useful for facilitating the crosslinking of such
siloxanes. The catalyst can be a metal-containing or non-metallic
compound. Examples of useful metal-containing compounds include
those of tin, titanium, zirconium, lead, iron cobalt, antimony,
manganese, bismuth and zinc.
In one embodiment of the present invention, tin-containing
compounds useful as crosslinking catalysts include:
dibutyltindilaurate, dibutyltindiacetate, dibutyltindimethoxide,
tinoctoate, isobutyltintriceroate, dibutyltinoxide, soluble dibutyl
tin oxide, dibutyltin bis-diisooctylphthalate, bis-tripropoxysilyl
dioctyltin, dibutyltin bis-acetylacetone, silylated dibutyltin
dioxide, carbomethoxyphenyl tin tris-uberate, isobutyltin
triceroate, dimethyltin dibutyrate, dimethyltin di-neodecanoate,
triethyltin tartarate, dibutyltin dibenzoate, tin oleate, tin
naphthenate, butyltintri-2-ethylhexylhexoate, tinbutyrate,
diorganotin bis .beta.-diketonates, and the like. Useful
titanium-containing catalysts include: chelated titanium compounds,
e.g., 1,3-propanedioxytitanium bis(ethylacetoacetate),
di-isopropoxytitanium bis(ethylacetoacetate), and tetraalkyl
titanates, e.g., tetra n-butyl titanate and tetra-isopropyl
titanate. In yet another embodiment of the present invention,
diorganotin bis .beta.-diketonates is used for facilitating
crosslinking in silicone sealant composition.
The curable composition of the present invention includes at least
one organic nanoclay filler (d). Nanoclays possess a unique
morphology with one dimension being in the nanometer range. The
nanoclays can form chemical complexes with an intercalant that
ionically bonds to surfaces in between the layers making up the
clay particles. This association of intercalant and clay particles
results in a material which is compatible with many different kinds
of host resins permitting the clay filler to disperse therein.
The term "exfoliation" as used herein describes a process wherein
packets of nanoclay platelets separate from one another in a
polymer matrix. During exfoliation, platelets at the outermost
region of each packet cleave off, exposing more platelets for
separation.
The term "gallery" as used herein describes the space between
parallel layers of clay platelets. The gallery spacing changes
depending on the nature of the molecule or polymer occupying the
space. An interlayer space between individual nanoclay platelets
varies, again depending on the type of molecules that occupy the
space.
The term "intercalant" as used herein includes any inorganic or
organic compound that is capable of entering the clay gallery and
bonding to its surface.
The term "intercalate" as used herein designates a clay-chemical
complex wherein the clay gallery spacing has increased due to the
process of surface modification. Under the proper conditions of
temperature and shear, an intercalate is capable of exfoliating in
a resin matrix.
The expression "low permeability to gas(es)" as applied to the
cured composition of this invention shall be understood to mean an
argon permeability coefficient of not greater than about 900
barrers (1 barrer=10.sup.-10 (STP)/cm sec(cmHg)) measured in
accordance with the constant pressure variable-volume method at a
pressure of 100 psi and temperature of 25.degree. C.
The expression "modified clay" as used herein designates a clay
material that has been treated with any inorganic or organic
compound that is capable of undergoing ion exchange reactions with
the cations present at the interlayer surfaces of the clay.
The term "nanoclay" as used herein describes clay materials that
possess a unique morphology with one dimension being in the
nanometer range. Nanoclays can form chemical complexes with an
intercalant that ionically bonds to surfaces in between the layers
making up the clay particles. This association of intercalant and
clay particles results in a material which is compatible with many
different kinds of host resins permitting the clay filler to
disperse therein.
The expression "organic nanoclay" as use herein describes a
nanoclay that has been treated or modified with an organic
intercalant.
The term "organoclay" as used herein designates a clay or other
layered material that has been treated with organic molecules
(variously referred to as "exfoliating agents," "surface modifiers"
or "intercalants") that are capable of undergoing ion exchange
reactions with the cations present at the interlayer surfaces of
the clay.
The nanoclays can be natural or synthetic materials. This
distinction can influence the particle size and for this invention,
the particles should have a lateral dimension of between about 0.01
.mu.m and about 5 .mu.m, and preferably between about 0.05 .mu.m
and about 2 .mu.m, and more preferably between about 0.1 .mu.m and
about 1 .mu.m. The thickness or the vertical dimension of the
particles can in general vary between about 0.5 nm and about 10 nm
and preferably between about 1 nm and about 5 nm.
Useful nanoclays for providing the organic nanoclay filler
component of the composition of the invention include natural or
synthetic phyllosilicates, particularly smectic clays such as
montmorillonite, sodium montmorillonite, calcium montmorillonite,
magnesium montmorillonite, nontronite, beidellite, volkonskoite,
laponite, hectorite, saponite, sauconite, magadite, kenyaite,
sobockite, svindordite, stevensite, talc, mica, kaolinite,
vermiculite, halloysite, aluminate oxides, or hydrotalcites, and
the like, and their mixtures. In another embodiment, useful
nanoclays include micaceous minerals such as illite and mixed
layered illite/smectite minerals such as rectorite, tarosovite,
ledikite and admixtures of illites with one or more of the clay
minerals named above. Any swellable layered material that
sufficiently sorbs the organic molecules to increase the interlayer
spacing between adjacent phyllosilicate platelets to at least about
5 angstroms, or to at least about 10 angstroms, (when the
phyllosilicate is measured dry) can be used in producing the filler
component to provide the curable composition of the invention.
In one embodiment of the present invention, organic compounds that
are useful for treating nanoclays and layered materials to provide
the filler component herein include cationic surfactants such as
ammonium, ammonium chloride, alkylammonium (primary, secondary,
tertiary and quaternary), phosphonium or sulfonium derivatives of
aliphatic, aromatic or arylaliphatic amines, phosphines or
sulfides.
Other organic treating agents for nanoclays that can be used herein
include amine compounds and/or quaternary ammonium compounds
R.sup.6R.sup.7R.sup.8N.sup.+X.sup.- each independently is an alkoxy
silane group, alkyl group or alkenyl group of up to 60 carbon atoms
and X is an anion such as Cl.sup.-, F.sup.-, SO.sub.4.sup.-,
etc.
Optionally, the curable composition herein can also contain at
least one solid polymer (e) having a permeability to gas that is
less than the permeability of the crosslinked diorganopolysiloxane.
Suitable polymers include polyethylenes such as low density
polyethylene (LDPE), very low density polyethylene (VLDPE), linear
low density polyethylene (LLDPE) and high density polyethylene
(HDPE); polypropylene (PP), polyisobutylene (PIB), polyvinyl
acetate(PVAc), polyvinyl alcohol (PVoH), polystyrene,
polycarbonate, polyester, such as, polyethylene terephthalate
(PET), polybutylene terephthalate (PBT), polyethylene napthalate
(PEN), glycol-modified polyethylene terephthalate (PETG);
polyvinylchloride (PVC), polyvinylidene chloride, polyvinylidene
floride, thermoplastic polyurethane (TPU), acrylonitrile butadiene
styrene (ABS), polymethylmethacrylate (PMMA), polyvinyl fluoride
(PVF), Polyamides (nylons), polymethylpentene, polyimide (PI),
polyetherimide (PEI), polether ether ketone (PEEK), polysulfone ,
polyether sulfone, ethylene chlorotrifluoroethylene,
polytetrafluoroethylene (PTFE), cellulose acetate, cellulose
acetate butyrate, plasticized polyvinyl chloride, ionomers
(Surtyn), polyphenylene sulfide (PPS), styrene-maleic anhydride,
modified polyphenylene oxide (PPO), and the like and mixture
thereof.
The optional polymer(s) can also be elastomeric in nature, examples
include, but are not limited to ethylene- propylene rubber (EPDM),
polybutadiene, polychloroprene, polyisoprene, polyurethane (TPU),
styrene-butadiene-styrene (SBS), styrene-ethylene-butadiene-styrene
(SEEBS), polymethylphenyl siloxane (PMPS), and the like.
These optional polymers can be blended either alone or in
combinations or in the form of coplymers, e.g. polycarbonate-ABS
blends, polycarbonate polyester blends, grafted polymers such as,
silane grafted polyethylenes, and silane grafted polyurethanes.
In one embodiment of the present invention, the curable composition
contains a polymer selected from the group consisting of low
density polyethylene (LDPE), very low density polyethylene (VLDPE),
linear low density polyethylene (LLDPE), high density polyethylene
(HDPE), and mixtures thereof. In another embodiment of the
invention, the curable composition has a polymer selected from the
group consisting of low density polyethylene (LDPE), very low
density polyethylene (VLDPE), linear low density polyethylene
(LLDPE), and mixture thereof. In yet another embodiment of the
present invention, the optional polymer is a linear low density
polyethylene (LLDPE).
The curable composition can contain one or more other fillers in
addition to organic nanoclay component (d). Suitable additional
fillers for use herein include precipitated and colloidal calcium
carbonates which have been treated with compounds such as stearic
acid or stearate ester; reinforcing silicas such as fumed silicas,
precipitated silicas, silica gels and hydrophobized silicas and
silica gels; crushed and ground quartz, alumina, aluminum
hydroxide, titanium hydroxide, diatomaceous earth, iron oxide,
carbon black, graphite, mica, talc, and the like, and mixtures
thereof.
The curable composition of the present invention can also include
one or more alkoxysilanes as adhesion promoters. Useful adhesion
promoters include N-2-aminoethyl-3-aminopropyltriethoxysilane,
.gamma.-aminopropyltriethoxysilane,
.gamma.-aminopropyltrimethoxysilane, aminopropyltrimethoxysilane,
bis-.gamma.-trimethoxysilypropyl)amine,
N-phenyl-.gamma.-aminopropyltrimethoxysilane,
triaminofunctionaltrimethoxysilane,
.gamma.-aminopropylmethyldiethoxysilane,
.gamma.-aminopropylmethyldiethoxysilane,
methacryloxypropyltrimethoxysilane,
methylaminopropyltrimethoxysilane,
.gamma.-glycidoxypropylethyldimethoxysilane,
.gamma.-glycidoxypropyltrimethoxysilane,
.gamma.-glycidoxyethyltrimethoxysilane,
.beta.-(3,4-epoxycyclohexyl)propyltrimethoxysilane,
.beta.-(3,4-epoxycyclohexyl) ethylmethyldimethoxysilane,
isocyanatopropyltriethoxysilane,
isocyanatopropylmethyldimethoxysilane,
.beta.-cyanoethyltrimethoxysilane,
.gamma.-acryloxypropyltrimethoxysilane,
.gamma.-methacryloxypropylmethyldimethoxysilane,
4-amino-3,3,-dimethylbutyltrimethoxysilane, and
N-ethyl-3-trimethoxysilyl-2-methylpropanamine, and the like. In one
embodiment, the adhesion promoter can be a combination of
n-2-aminoethyl-3-aminopropyltrimethoxysilane and
1,3,5-tris(trimethoxysilylpropyl)isocyanurate.
The compositions of the present invention can also include one or
more non-ionic surfactants such as polyethylene glycol,
polypropylene glycol, ethoxylated castor oil, oleic acid
ethoxylate, alkylphenol ethoxylates, copolymers of ethylene oxide
(EO) and propylene oxide (PO) and copolymers of silicones and
polyethers (silicone polyether copolymers), copolymers of silicones
and copolymers of ethylene oxide and propylene oxide and mixtures
thereof.
The curable compositions of the present invention can include still
other ingredients that are conventionally employed in RTC
silicone-containing compositions such as colorants, pigments,
plasticizers, antioxidants, UV stabilizers, biocides, etc., in
known and conventional amounts provided they do not interfere with
the properties desired for the cured compositions.
The amounts of silanol-terminated diorganopolysiloxane(s),
crosslinker(s), crosslinking catalyst(s), oranic nanoclay(s),
optional solid polymers(s) of lower gas permeability than the
crosslinked diorganopolysiloxane(s), optional filler(s) other than
organic nanoclay, optional adhesion promoter(s) and optional ionic
surfactant(s) can vary widely and, advantageously, can be selected
from among the ranges indicated in the following table.
TABLE-US-00001 TABLE 1 Ranges of Amounts (Weight Percent) of
Components of the Curable Composition of the Invention Components
of the First Second Third Curable Composition Range Range Range
Silanol-terminated 50-99 70-99 80-85 Diorganopolysiloxane(s)
Crosslinker(s) 0.1-10 0.3-5 0.5-1.5 Crosslinking Catalyst(s)
0.001-1 0.003-0.5 0.005-0.2 Organic Nanoclay(s) 0.1-50 10-30 15-20
Solid Polymer(s) of Lower 0-50 5-40 10-35 Gas Permeability than
Crosslinked Dioganopoly- Siloxane(s) Filler(s) other than 0-90 5-60
10-40 Organic Nanoclay Silane Adhesion Promoter(s) 0-20 0.1-10
0.5-2 Ionic Surfactant(s) 0-10 0.1-5 0.5-0.75
The curable compositions herein can be obtained by procedures that
are well known in the art, e.g., melt blending, extrusion blending,
solution blending, dry mixing, blending in a Banbury mixer, etc.,
in the presence of moisture to provide a substantially homogeneous
mixture.
Preferably, the methods of blending the diorganopolysiloxane
polymers with polymers may be accomplished by contacting the
components in a tumbler or other physical blending means, followed
by melt blending in an extruder. Alternatively, the components can
be melt blended directly in an extruder, Brabender or any other
melt blending means.
The invention is illustrated by the following non-limiting
examples.
COMPARATIVE EXAMPLE 1 AND EXAMPLES 1-4
A mixture of silanol-terminated polydimethylsiloxanes (PDMS),
specifically, Silanol 5000, a silanol-terminated
polydimethylsiloxane of 5000 cs nominal and Silanol 50,000, a
silanol-terminated polydimethylsiloxane of 50,000 cs nominal, both
available from Gelest, Inc., were mixed in a 100 ml cup with
Cloisite 15A ("C-15A," a montmorillonite clay modified with 125
milliequivalants of dimethyl dehydrogenated tallow ammonium
chloride per 100 g of clay available from Southern Clay Products)
or SF ME100 (a synthetic fluorohectorite having the general formula
NaMg.sub.2.5Si.sub.4O.sub.10(F.sub..alpha.OH.sub.1-.alpha.).sub.2
(0.8<=.alpha.<=1.0) available from Unicorp, Japan) employing
a hand blender for 10-15 minutes and thereafter placed in a vacuum
dessicator for 5 minutes to remove air bubbles generated during
mixing. Blends were made with the amounts of nanoclay ranging from
1 to 10 weight percent.
Following the foregoing procedure, curable compositions of the
following Examples were obtained: Comparative Example 1: 50 grams
mix (Silanol 5000 and Silanol 50000@50:50) Example 1: 48.75 grams
mix (Silanol 5000 and Silanol 50000@50:50)+1.25 grams of Cloisite
C-15A clay Example 2: 47.5 grams mix (Silanol 5000 and Silanol
50000@50:50)+2.5 grams of Cloisite C-15A clay Example 3: 45 grams
mix (Silanol 5000 and Silanol 50000@50:50)+5 grams of Cloisite
C-15A clay Example 4: 45 grams mix (Silanol 5000 and Silanol
50000@50:50)+5 grams of SF ME100 clay
The above-indicated blends were then used to make cured sheets as
follows: PDMS-nanoclay formulations were mixed with n-propyl
silicate ("NPS," a crosslinker) and solubilized dibutyl tin oxide
("DBTO," a crosslinking catalyst), as listed in Table 2, using a
hand blender for 5-7 minutes with air bubbles being removed by
vacuum. Each blend was poured into a Teflon sheet-forming mold and
maintained for 24 hours under ambient conditions (25.degree. C. and
50% humidity) to partially cure the PDMS components. The partially
cured sheets were removed from the mold after 24 hours and
maintained at ambient temperature for seven days for complete
curing.
TABLE-US-00002 TABLE 2 Curable Compositions wt % wt % grams NPS
DBTO Comparative Example 1: Silanol 50 2 1.2 mixture Example 1:
Silanol mixture with 50 2 1.2 2.5 wt % C-15A Example 2: Silanol
mixture with 50 2 1.2 5 wt % C-15A Example 3: Silanol mixture with
50 2 1.2 10 wt % C-15A Example 4: Silanol mixture with 50 2 1.2 10
wt % SF ME100
The argon permeability of the foregoing curable compositions was
measured using a gas permeability set-up. The measurements were
based on the variable-volume method at 100 psi pressure and at a
temperature of 25.degree. C. The permeability measurements were
repeated under identical conditions 2-3 times in order to assure
their reproducibility.
The permeability data are graphically presented in FIGS. 1 and
2.
COMPARATIVE EXAMPLE 2 AND EXAMPLES 5-9
To provide a 1 weight percent C-15A clay (see Example 5, Table 3):
227.7 g of OMCTS (octamethylcyclotetrasiloxane) and 2.3 g of C-15A
were introduced into a three-neck round bottom flask fitted with
overhead stirrer and condenser. The mixture was stirred at 250 rpm
for 6 hours at ambient temperature. The temperature was increased
to 175.degree. C. while stirring was continued. 0.3 g of CsOH in 1
ml of water was added to the reaction vessel through a septum.
After 15 minutes, polymerization of OMCTS began and 0.5 ml of water
was then added with an additional 0.5 ml of water being added after
5 minutes. Heating and stirring were continued for 1 hour after
which 0.1 ml of phosphoric acid was added for neutralization. The
pH of the reaction mixture was determined after 30 minutes.
Stirring and heating were continued for another 30 minutes and the
pH of the reaction mixture was again determined to assure complete
neutralization. Distillation of cyclics was carried out at
175.degree. C. and the mixture was thereafter cooled to room
temperature.
The same procedure was followed with 2.5, 5 and 10 wt % of C-15A
(see Examples 6-8, Table 3).
Similar in-situ polymerization procedures were followed with 10 wt
% high aspect ratio clay (SF ME100) (see Example 9, Table 3). The
in-situ polymer with different amounts of clay were then used to
make cured sheets as follows: In-situ PDMS-nanoclay formulations
were mixed with NPS crosslinker and solubilized DBTO catalyst using
a hand blender for 5-7 min with air bubbles being removed by
vacuum. The mixture was then poured into a Teflon sheet-forming
mold and maintained for 24 hours under ambient conditions
(25.degree. C. and 50% humidity). The partially cured sheets were
removed from the mold after 24 hours and maintained at ambient
temperature for seven days for complete curing.
TABLE-US-00003 TABLE 3 Curable Compositions wt % wt % grams NPS
DBTO Comparative Example 2: Silanol mixture 50 2 1.2 Example 5:
In-situ silanol with 1 wt % 50 2 1.2 C-15A Example 6: In-situ
silanol with 2.5 wt % 50 2 1.2 C-15A Example 7: In-situ silanol
with 5 wt % 50 2 1.2 C-15A Example 8: In-situ silanol with 10 wt %
50 2 1.2 C-15A Example 9: In-situ silanol with 10 wt % 50 2 1.2 SF
ME100
Argon permeability was measured using a gas permeability set-up as
in the previous examples. The measurements were based on the
variable-volume method at 100 psi pressure and at a temperature of
25.degree. C. Measurements were repeated under identical conditions
2-3 times in order to assure their reproducibility.
The permeability data are graphically presented in FIGS. 1 and 2.
As shown in the data, argon permeability in the case of the cured
sealant compositions of the invention (Examples 1-3 and 5-8 of FIG.
1 and Examples 4 and 9 of FIG. 2) was significantly less than that
of cured sealant compositions outside the scope of the invention
(Comparative Examples 1 and 2 of FIGS. 1 and 2). In all, while the
argon permeability coefficients of the sealant compositions of
Comparative Examples 1 and 2 exceed 900 barrers, those of Examples
1-9 illustrative of sealant compositions of this invention did not
exceed 900 barrers and in some cases, were well below this level of
argon permeability coefficient (see, in particular, examples 3, 8
and 9).
While preferred embodiments of the present invention has been
illustrated and described in detail, various modifications of, for
example, components, materials and parameters, will become apparent
to those skilled in the art, and it is intended to cover in the
appended claims all such modifications and changes which come
within the scope of this invention.
* * * * *